1. Field of the Invention
The present invention relates to a multi-gear-speed transmission in which a plurality of drive gears and a plurality of driven gears are supported respectively on parallel gear shafts in the state of being normally meshed on a gear speed basis.
2. Description of Background Art
The normally meshed type multi-gear-speed transmission has a configuration in which the gears on one hand of the drive gears and the driven gears are fixed on a gear shaft, whereas the gears on the other hand of the drive gears and the driven gears are rotatably borne on another gear shaft, and that one of the rotatably borne gears which is engaged with the rotary shaft is changed over by engaging means, to thereby make a gear shift.
There is a patent application which has been filed by the present applicant and granted a patent, in which cam member-driven engaging pawls are used for the engagement between the gear and the gear shaft in such a configuration as above.
The transmission disclosed in Japanese Patent No. 3838494 has a structure in which a cam member (clutch operating element) provided with a cam groove is moved in the axial direction inside a hollow gear shaft (transmission shaft) rotatably bearing gears thereon, whereby pin members supported in the state of penetrating a side wall of the hollow gear shaft are moved up or down to cause free ends of ratchet pawls fitted in an inner peripheral part of the gear to project or retract from the inner peripheral surface. When the free ends of the ratchet pawls are projected, they are engaged with gear teeth formed in the hollow gear shaft so as to transmit rotation in one direction, and when the ratchet pawls are retracted, the engagement is released.
Each of the gears is provided in its inner peripheral part with recessed parts for accommodating the ratchet pawls, and the ratchet pawls are swingably fitted in the recessed parts so that their free ends can project or retract from the inner peripheral surface.
For each of the gears, two such ratchet pawls are provided.
Therefore, the structure is complicated. In addition, at the time of mounting the plurality of gears to the gear shaft, the gears must be fitted over the gear shaft while keeping the ratchet pawls contained in the two recessed parts of the inner peripheral part of each of the gears so that their free ends will not project from the inner peripheral surface of the gear. In this case, the pin members must be preliminarily inserted in radially penetrating through-holes provided in the gear shaft in plurality in the circumferential direction, in such a state as not to interfere with the gears.
The operation of fitting the gears over the gear shaft in the condition where the ratchet pawls are thus respectively contained in the two recessed parts of the inner peripheral part of each of the gears may need use of some jig(s) and is not easy to carry out. In addition, on the side of the gear shaft, the condition where the plurality of pin members are inserted in plurality in the circumferential direction has to be maintained during the operation. This further increases the difficulty in carrying out the operation.